Antennas are utilized for communication, navigation, and surveillance. Aircrafts rely on communication navigation, and surveillance. Special considerations are considered when utilizing an antenna on an aircraft and/or other moving vehicles and devices.
Log periodic antennas (also known as log periodic arrays) are multi-element broad band, unidirectional, narrow-beam, antennas with impedance and radiation characteristics that are regularly repetitive as a logarithmic function of the excitation frequency. Arrays of multielement Log periodic antennas have similar performance but with increased directivity in one plane due to the arraying of individual log periodic antenna with a prescribed phase relationship. The elements may be dipoles within the log periodic array. Log periodic dipole arrays are driven in free space and cannot be close to a local ground and are therefore, non-conformal and/or cannot be mounted flush with a metallic structure.
Dipole log periodic antennas are difficult to drive against the ground. A log periodic scaled monopole array may be in an end fire configuration, but the log periodic scaled monopole array is non-conformal due to the height of the individual monopole elements that comprise the array. The height of this array is one quarter of the wavelength being transmitted and/or received (to the first order) at the lowest operating frequency of the array. Log periodic antenna-based phased arrays may be in an end fire configuration, but the log periodic phased arrays are, also, non-conformal. Microstrip broadside log periodic antennas and other types of planar log periodic arrays have broadside rather than end fire performance.